1. Field of the Invention
The present invention relates to an electronic device and convex member for a circuit board, and more particularly to an electronic device and convex member holding up a circuit board in a housing.
2. Description of the Related Art
At present, laptops (i.e., portable microcomputers) are designed to be compact, light in weight and easy to carry. Such a portable microcomputer (called the “microcomputer”) may be dropped while it is carried by a user. When dropped, a housing of the microcomputer may be deformed and undergo dropping impacts or external static loads.
It is assumed that a circuit board is fixedly mounted in the housing. If moments caused by the deforming housing are transmitted to the circuit board, the circuit board will be gradually warped. In such a case, interconnections on the circuit board and joints between the circuit board and semiconductor chips will be broken or damaged.
Especially, when the circuit board is made of materials having low rigidity in order to meet weight and thickness saving requirements, there is a large difference between the rigidity of the circuit board and that of elements mounted thereon. Therefore, the mounted elements will become defective when the circuit board is deformed.
In order to overcome the foregoing problem, a resin material is inserted between the circuit board and elements mounted thereon, thereby locally enhancing joints of the circuit board and elements. This measure is called the under-filling method. Refer to the Japanese patent No. 3,348,973.
However, it is very difficult in the foregoing method to exchange elements mounted on the circuit board. Further, the circuit board itself has to be exchanged when mounted elements are found to be defective. Therefore, the method is considered to be insufficient as a countermeasure.
Further, it has been proposed to support a circuit board using springs. In this case, cylindrical supports are fitted in openings on the circuit board. Each cylindrical support has one end thereof fixed to a housing, and has a flange on a side surface thereof. The circuit board is supported by springs inserted in the flanges of the cylindrical supports. This structure protects the circuit board against moments caused by the deformation of the housing.
However, the circuit board tends to be displaced in a direction which is vertical to the plane where elements are mounted. Especially, some connectors are directly mounted on the circuit board and extend outward via an open area of the housing. Further, the connectors have to be fixed to the housing in order that cables or the like are reliably attached to and detached from the connectors. In such a case, the connectors are a little bit displaced while the circuit board tends to be extensively displaced. Since the connectors and the circuit board are displaced in different amounts, joints between the connectors and the circuit board undergo an excessive deformation. Poor connections will be caused at the joints where the connectors and the circuit board are connected.